Time-gated CMOS SPAD and a Quantum Well Laser Diode with a CMOS Driver for Time-Resolved Diffuse Optics Imaging

Single-Photon Avalanche Photodiodes (SPADs) were fabricated and characterized in 150 nm CMOS technology. The SPAD is based on a p+/nwell junction with a p-substrate guard ring. In addition, a compact gain switched quantum well (QW) laser diode with a CMOS driver was used with the proposed SPAD for time-resolved diffuse optics measurements. The measured impulse response function (IRF) of the SPADs was ~50 ps at best. Two phantoms were measured to demonstrate the suitability of SPADs for time-resolved diffuse optics imaging (TRDOI).